A typical example of road-to-vehicle communication services are services to assist prevention of vehicle collision (i.e., traffic accident) at a crossing as disclosed, for example, in Japanese patent publication no. 2002-225619 entitled “Vehicle Drive Assisting System under Dark Environment”. This is a service to generate warning to pedestrians or drivers who drive vehicles in one direction toward a crossing under poor visible conditions when another vehicle approaches the crossing in another direction. It is to be noted that most conventional road-to-vehicle communication systems employ different communication systems or schemes in communication media and frequency such as VICS (Vehicle Information & Communication System), DSRC (Dedicated Short Range Communication) or the like depending upon locations (national roads, local roads, crossings, etc.).
In other words, when providing road-to-vehicle communication services, it is generally very difficult to provide services by applying the same communication systems at all roads and crossings from the beginning. It is therefore unavoidable that various kinds of communication systems for applying road-to-vehicle communication services are intermingled.
In case of various kinds of intermingled communication systems as described hereinabove, it is typical that each road-to-vehicle communication equipment should be equipped with all functions to cope with all communication systems (i.e., communication media and communication frequencies) for conventional as well as more recent communication systems and that all of the communication functions must be made in a stand-by state all the time, thereby wasting power. Moreover, if there are a large number of installed communication systems, it takes some time to switch them from a stand-by condition to an active condition. This means that activation of a proper communication function is too late for preventing a traffic accident or an anti-collision support service is not available unless the driver manually switches the communication frequencies.